score:5
This is not possible. MileagePlus accounts are strictly tied to individual people, and only the member who flew can accrue miles. The name on your account must match the name on your ticket, and the name on your ticket must match a government-issued ID. This is true whether you're flying on a United-operated flight or one operated by a partner.
It is possible to pay to transfer miles between accounts, but the fees are quite hefty and can easily approach the approximate value of the miles.
This applies to most airlines, but a handful have exceptions, with particular rules and conditions. For example, British Airways has Household Accounts, Emirates has Family Bonus members, JetBlue has Family Pooling, and Asiana has the Family Mileage Plan and Mileage Transfer. As Asiana is a Star Alliance airline, it might be possible for you to all open accounts over there, if you're all family members, but those miles would be separate from those in your MileagePlus accounts and wouldn't help you gain status on United.